But if the spirit is willing, the body is lagging badly behind in the effort.

Although exercise is one of the best ways to tone up and trim down, just 20 percent of Americans engage in the proper amount of activity, according to the Centers for Disease Control and Prevention.

To be fair, it is likely that many of us have tried to exercise, only to have gotten discouraged when little or no weight loss occurred. But such disappointment may simply be a result of choosing the wrong activity.

Following are nine exercises that science has identified as true calorie-burners. And as an added bonus for those deterred by the thought of a pricey gym membership, all of these activities are low cost or no cost.

All calorie measurements come from the Mayo Clinic and represent the amount of calories burned at three different weight levels.

1. Jumping rope

Jumping rope not only tops our list of weight-loss exercises, but it's also among the most economical ways to whittle your waistline. You can purchase a high-quality jump rope for $10 or less. According to WebMD:

You'd have to run an eight-minute mile to work off more calories than you'd burn jumping rope.

Plus, jump ropes are perfectly portable, allowing you to easily switch up your scenery. They may even bring you back to your childhood!

Calories burned:

861 (160 pounds)

1,074 (200 pounds)

1,286 (240 pounds)

2. Running

Running is another great and economical way to help shed unwanted pounds. According to Runner's World:

It probably takes you less than 10 minutes to run off 100 calories — a rate that leaves most other forms of exercise in the dust.

Obviously, running faster should result in a better burn, but every time your foot hits the pavement or trail, you're taking a step in the right direction. The cost: approximately $50 for a decent pair of running shoes.

Calories burned (running at 8 mph):

861 (160 pounds)

1,074 (200 pounds)

1,286 (240 pounds)

3. Swimming

Make a splash in the water, and it will translate to the scale. According to Fitday.com:

Swimming is one of the best forms of cardiovascular exercise because it works the entire body, but also provides a low-impact form of exercise. Regardless of your swimming ability, with some practice, you should be able to hit the pool and lose some weight when swimming.

The more vigorous your laps, the more calories you'll torch. Look for free ways to brush up on your backstroke — like at a swimming pool in a friend's backyard, a local lake or the ocean.

Calories burned:

715 (160 pounds)

892 (200 pounds)

1,068 (240 pounds)

4. Climbing stairs

When it comes to achieving your weight-loss goals, climbing stairs can really give you a leg up. According to Shape:

Climbing stairs is one of the best ways to stay healthy because it increases cardiovascular levels and bone mass, making it an ideal choice for preventive medicine. Just ask your doctor for a fitness program, and he will have you walking up the stairs.

You don't need to spring for fancy equipment or a pricey gym membership. Instead, climb stairs in your home, at your office or anywhere else you encounter them.

Calories burned (stair treadmill):

657 (160 pounds)

819 (200 pounds)

981 (240 pounds)

Related: 15 things you should stop wasting your money on

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15 things you can stop wasting your money on

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9 best low-cost exercises for weight loss

1. Cable TV

With the advent of Hulu, Netflix, Amazon Instant Video, and Apple TV, there's hardly a reason to splurge on a fancy DVR system or even basic cable — so long as you're willing to be patient.

Most shows are added at least 24-hours after airing and some networks won't give them up until eight days.

"If you travel abroad often, make sure you use credit cards without foreign transaction fees, otherwise you'll be paying an extra 3% to 5% on all your purchases."

Via Business Insider

Photo Credit: Getty

3. Extended warranties

Retailers push hard to sell you extended warranties — and conveniently pump up their sales figures at the same time.

Don't do it, Schrage warns.

"The only instance I'd recommend a warranty is in the case of a laptop. Otherwise, the warranties themselves can often cost as much as simply buying a used or new replacement for your item, or repairing it," he adds.

Via Business Insider

Photo Credit: Getty

4. The roof over your head

If you're blowing most of your income on a loft in Midtown, you're making a big mistake, says Jeremy Gregg, executive director of the PLAN Fund.

When buying a new cell phone, Sethi likes to pay a little bit more upfront by choosing the unlimited data and text messaging plan. He then sets a three-month check-in on his calendar, and analyzes his spending patterns after a few months to see where he can cut back.

You can use this method for any usage-based services, he says.

Via Business Insider

Photo Credit: Getty

6. Online shipping

Nearly all retailers offer some sort of option that gets your purchases to your doorstep without additional fees.

Zappos and L.L. Bean are among the rarest breed of businesses offering free shipping on every single purchase, but most companies will demand a minimum purchase.

To help track down deals on shipping, use Freeshipping.org. The site stores information on expiration dates, tells you much to spend to qualify, and lets you search by store name or product.

Personal finance expert Dani Johnson suggests you think twice before rushing out to buy Dad another tie this Christmas.

"You should make a pact with your friends and family to give back instead," Johnson says. "Pool a percentage of money you were going to spend on gifts and give a secret blessing to somebody who is truly in need."

Weight loss pills and supplements marketed as miracles for overweight couch potatoes are most likely traps.

"Not only are there enough pills and potions that you could start a new one each week, but the negative effects on your health outweighs the money you will waste," says nutritionist Rania Batayneh.

"This is a billion dollar industry and the truth is that a lean body does not come in a pill," Batayneh says.

Via Business Insider

Photo Credit: Getty

12. Lottery tickets

"Sure, you can (buy a lottery ticket) every once in a while just for fun, but never make a lottery purchase with any real expectation of winning," Schrage warns.

"The odds are significantly stacked against you, and why waste your hard-earned money on lottery tickets when you could be saving for retirement or treating yourself to a nice meal?"

Via Business Insider

Photo Credit: Getty

13. Brand new cars

"People get bored with cars quickly. They always want a new car and so they're always dealing with a car payment," says certified financial planner Michael Egan. "But it's a hugely depreciating asset. You don't want to be putting a lot of money into something that's going to be worth nothing after a certain number of years."

Look for used car options, which could save you a substantial amount of money. Check out Kelley Blue Book to get an idea of how much you should pay for a used car.

Another option is leasing a car. You can determine whether or not this is a good option for you by following this flow chart.

Via Business Insider

Photo Credit: Getty

14. Subscriptions

Subscriptions — to magazines, newspapers, and the gym — can add up, and oftentimes, we don't use them as much as we had originally planned.

Sethi recommends implementing what he calls the 'à la carte' method, which takes advantage of psychology to cut our costs.

"Cancel all the discretionary subscriptions you can: your magazines, TiVo, cable — even your gym," Sethi explains in "I Will Teach You To Be Rich." "Then, buy what you need à la carte. Instead of paying for a ton of channels you never watch on cable, buy only the episodes you watch for $1.99 each off iTunes. Buy a day pass for the gym each time you go."

It works for three reasons, Sethi writes: You're likely overpaying already, you're forced to be conscious about your spending, and you value what you pay for.

Shooting hoops can also help you lower the needle on the scale, according to Livestrong.com:

Playing basketball can help you burn excess calories when incorporated into your weight-loss nutrition plan. Running up and down a basketball court and shooting hoops offers plenty of exercise. Exercising drills that basketball players perform during practices will not only burn fat, but strengthen your muscles and improve your coordination as well.

Basketball prices vary, but we have seen them for under $10. So gather some friends or find a pick-up game and shoot for weight-loss success.

Calories burned:

584 (160 pounds)

728 (200 pounds)

872 (240 pounds)

6. Flag (or touch) football

Tossing around the old pigskin is not only fun, it's also a fabulous form of fitness, says Fitday.com:

Flag football is a group sport that engages your entire body. This high impact sport provides you with an intense cardiovascular workout. While out on the field, you will be running, sprinting and jogging, and that is all in just one play. This fast-paced game requires constant high-intensity actions that have you burning hundreds of calories per hour.

It's time to channel your inner Peyton Manning!

Calories burned:

584 (160 pounds)

728 (200 pounds)

872 (240 pounds)

7. Aerobics

Or, how about getting in touch with your inner Jane Fonda? According to Livestrong.com:

When combined with a low-calorie diet, aerobics can lead to significant weight loss...Gradually increase the duration and intensity of your aerobic workouts for even greater weight loss.

Are issues, such as joint pain, preventing you from getting physical? Try water aerobics, a great choice for those with arthritis, back problems, fibromyalgia, leg injuries and other conditions.

Calories burned (high-impact aerobics):

533 (160 pounds)

664 (200 pounds)

796 (240 pounds)

8. Backpacking

Want a great weight-loss activity you can enjoy on your own or with a group of friends? Consider backpacking. You likely won't even realize the pounds are melting off as you take in your surroundings while toting around your gear.

Plus, you'll only have the provisions you brought along, eliminating fattening food temptations.

Calories burned:

511 (160 pounds)

637 (200 pounds)

763 (240 pounds)

9. Hiking

The next time someone tells you to take a hike, listen to them. Hiking is a great workout for those who don't want to commit to backpacking. According to Health.com:

Few activities beat the body benefits of hiking; you're slipping cardio into your day and burning up to 530 calories per hour on the trail. And in gusty weather, the wind resistance can boost your burn potential by about 5 percent, experts say. It's a terrific total-body workout.

Now, who's ready to hit the trails?

Calories burned:

438 (160 pounds)

546 (200 pounds)

654 (240 pounds)

Do you know of other activities that can help you shed pounds? Share them in our Forums. It's a place where you can swap questions and answers on money-related matters, life hacks and ingenious ways to save.